Integrated circuits typically comprise large numbers of transistors, resistors, capacitors, diodes, interconnects and other such devices formed within a small area on a semiconductor substrate. Each of these circuit devices may generate heat while the integrated circuit is operating. If this heat generation is not counterbalanced by heat dissipation, the temperature may rise in the integrated circuit to the point where performance is degraded, and even to a point where physical damage to the integrated circuit may occur. As a result, the ability to accurately track the thermal conditions of an integrated circuit is paramount with respect to reliability, functionality and design optimization.
Making things more difficult is the fact that heat is not uniformly generated across a typical integrated circuit. Instead, a modem integrated circuit will usually be divided into a number of functional units that occupy different regions. These functional units are frequently not used equally. For example, a certain application may utilize logic circuitry more than memory circuitry. As a result, some regions of an integrated circuit will tend to generate heat faster than others. What is more, variations in production processes, feedback between circuit devices and other unintended phenomena may also cause regions of an integrated circuit to have higher operating temperatures. The relatively hotter regions are conventionally called “hot spots.”
It is known that one or more temperature sensors may be added to an integrated circuit in order to monitor temperature and mitigate the detrimental effects of hot spots. See, for example, U.S. Patent Application No. 2005/0166166, entitled “Method and Apparatus for Thermal Testing of Semiconductor Chip Designs,” U.S. Pat. No. 5,502,828, entitled “Temperature Management for Integrated Circuits,” and U.S. Patent Application No. 2006/0006166, entitled “On-Chip Power Supply Regulator and Temperature Control System.”
Conventional arrangements such as those described in the above-cited references have a number of disadvantages. For example, they typically require that temperature sensors be positioned in a central region of the integrated circuit, often close to predicted hot spots. Critical space must therefore be sacrificed for the temperature sensors, and the temperature sensors cannot be easily retrofitted onto previously designed integrated circuits. In addition, the temperature sensors in the above-cited references typically only yield data about those regions of the integrated circuit in the immediate vicinity of a temperature sensor. These methods, therefore, fail to provide broad coverage of the integrated circuit, and, as a result, unpredicted critical temperature events may go entirely undetected.
For the foregoing reasons, there is a need for methods and apparatus allowing the thermal conditions of an integrated circuit to be accurately tracked in real time without the attendant disadvantages found in the prior art.